We will use genome-wide genetic mapping, large-scale DNA arrays and high-throughout DNA sequencing to identify murine candidate genes that may play a role in early hematopoiesis in determining the frequency of hematopoietic stem cells. We will also help clone and sequence Drosophila genes that may be homologues of those controlling early murine hematopoiesis. Candidate genes will be tested and biological assays developed by our collaborators.